1. Field of the Invention
Aspects of the present invention relate to a rechargeable battery, and more particularly, to a rechargeable battery having a prismatic shape capable of not deforming under pressure.
2. Description of the Related Art
Recently, a large number of compact and light-weight electric or electronic apparatuses such as cellular phones, notebooks, and camcorders have been developed and produced. These portable electric or electronic apparatuses are provided with battery packs, so that these apparatuses can operate without separate power supplies. The battery pack includes at least one battery for outputting a voltage having a predetermined level to drive the portable electric or electronic apparatuses for a predetermined time.
Typically, the battery packs have employed a rechargeable batteries to provide economical efficiency. As representative examples of rechargeable batteries, there are nickel cadmium (Ni—Cd) batteries, nickel hydride (Ni—MH) batteries, and lithium rechargeable batteries such as lithium (Li) polymer batteries and lithium ion (Li-ion) batteries.
Particularly, a lithium rechargeable battery has an operating voltage of 3.6V, which is three times higher than that of a Ni—Cd battery or a Ni—MH battery. In addition, the lithium rechargeable battery has a high energy density per unit weight. Therefore, the demand for lithium rechargeable batteries has rapidly increased.
For lithium rechargeable batteries, a lithium-based oxide is used as a positive electrode active material, and carbon is used as a negative electrode active material. In general, the lithium rechargeable batteries are classified into liquid electrolyte batteries and polymer electrolyte batteries according to the type of electrolyte. A lithium rechargeable battery that uses a liquid electrolyte is called a lithium ion battery, and a lithium rechargeable battery that uses a polymer electrolyte is called a lithium polymer battery. Lithium rechargeable batteries are manufactured in various shapes and may be classified into a can-type battery, a prismatic battery, and a pouch-type battery according to the shapes.
In general, a lithium rechargeable battery is constructed with a case, a jelly-roll-type electrode assembly accommodated into the case, and a cap assembly covering the upper portion of the case.
The electrode assembly is constructed by rolling a positive electrode plate coated with a positive electrode active material, a negative electrode plate coated with a negative electrode active material, and a separator. The separator is interposed between the positive and negative electrode plates to prevent a short circuit between the two electrode plates and to allow only lithium ions (Li-ions) to pass through. In addition, an electrolyte solution is contained in the case to enable the lithium ions to move.
The cap assembly is engaged with the upper opening of the case where the electrode assembly is accommodated. The cap assembly is provided with a plate-shaped cap plate having the same size and shape as the opening of the case. A central portion of the cap plate is provided with a terminal hole through which an electrode terminal passes. A tube-shaped gasket is provided to surround the outside of the electrode terminal in order to electrically insulate the electrode terminal from the cap plate. An insulating plate is disposed on a bottom surface of the cap plate, and a terminal plate connected to the electrode terminal is disposed on a bottom surface of the insulating plate.
One side of the cap plate is provided with a safety vent to prevent an explosion due to a rise in pressure inside the case, and a protrusion protruding upwardly is provided around the safety vent to prevent resin injected into the upper portion of the cap plate from twisting due to external pressure. The upper portion of the protrusion is provided with an auxiliary protrusion to strengthen a supporting force for preventing torsion on the resin.
In addition, the top surface of the cap plate is provided with an insulating tape to insulate the electrode terminal from the cap plate.
However, the safety vent of a conventional rechargeable battery may be damaged by the resin injected into the upper portion of the cap plate.
Another disadvantage of a conventional rechargeable battery is that, after providing the insulating tape to the top surface of the cap plate, the upper portion of the protrusion is provided with the auxiliary protrusion, so that additional processes in production must be performed.